Core orientation apparatus



March 7, 1939.

J. M. PEARSON CORE ORIEN'IATON APPARATUS Filed June '7, 1937 Patented Mar.`7,193a l l 2,149,715

UNITED STATES PATENT OFFICE com; oRiEN'rA'rIoN APPARATUS John M, Pearson, Swarthmore, Pa., assignor to Sperry-Sun Well Surveying Company, Philadelphia, Pa., a corporation of Delaware Application June 7, 1937, serial No. 146,739 s claims. (01,.33-1) This invention relates to an apparatus for design in taking into account the various correctermining the dip and strike of strata appearing tions. in cores taken from a bore hole from data in- It is accordingly the object of the present including the magnetic polarity or susceptibility of vention to provide an apparatus on which the- 5 a` core, the inclination and direction of the bore various data may be set up and which, after ad-o hole at .the point where the core was taken, and justments in accordance with the various data, other auxiliary information. will give a true indication of the dip and strike of As described, for example, in Herrick Patent the bedding plane shown in a magnetically aniso- 1,792,639, dated February 17,-1931, it is p'ossible tropic core, in which the magnetic anisotropy l to determine to a fair degree of accuracy the dip may take the form of polarization or antisotropic l0 and strike of strata penetrated by a bore hole if susceptibility. Attempts have been made heremeasuremets are made to ascertain the magtofore to provide such apparatus, but magnetic netic polarization of a core taken at the location dip was not taken into account and, while such of the strata. apparatus would give fairly accurate results 'I'he assumption, borne out by observations, is under some conditions, it was quite possible that l5 that in a magnetically polarized core, the axis of by an unfortunate combination of circumstances polarization originally coincided in direction and involving the formation,- the magnetic dip and sense with the earths iield, and that in a core the slope of the bore hole errors of considerable showing an axis of maximum susceptibility, that magnitude could arise in the determination of axis coincided in direction withthe direction of the dip and strike. the earths eld, .though in the latter case the The above object and more specic objects of susceptibility axis is without sign. the invention, particularly relating to details,j In making such determinations, the magnetic will be apparent from the following description polarity or axis of maximum susceptibility of the read in conjunction with the accompanying core is determined by means of an apparatus Vdrawing in which: such as thatdisclosed in said Herrick patent, and Figure 1 is a side elevation, partly in section, the magnetic north or susceptibility axis of the showing the improved type of orientation appacore indicated thereon. ByYsuitable measure- 11342118;` J

ments there can then be determined the appar- Figure 2 iS allian- VieW 0f the Same with Cerent dip and strike-'ofl a beddingplane appearing tain Darts in hOI'iZOnal Section; 30 inthe core with respect to the magnetic north or Figure 3 is a fragmentary elevation of'certain Y susceptibility axis so indicated. of the parts of the apparatus ,directly associated For simplicity of expression, the magnetic po with the bedding plane plate; v larity, alone, will be usually referred to hereafter, Figure 4 is a fragmentary view showing thethough it willbe understood that the axis of arrangement for setting up the Value Ufthe 11158435 maximum susceptibility may be used instead of netic dip on the apparatus; and the axis of polarization, with the exception that Figure 5 is a section taken oni the plane indithe latter will 'give rise to two alternative results catedat 5-5 in Figure 1. Y from which the true one'must be chosen by ref- The apparatus comprises a rigid supporting 40 erence to other information. structure consisting of a horizontal base plate 2 o Obviously, however, the dips and strikes thus and a bracket i secured thereto. v The bracket 4 obtained are n'ot the true ones and various other Supports a; spindle 6, representing the axisv of factors must be considered before there can be a.` bore hole, by 'means of a ball and socket jointA A ascertained the actual value of the dips and indicated at 8 and comprising a ball member se.

strikes with respect to the true north. First there Acured .to the spindle 6 resting in a spherical de- 4;, 'I

must be considered the direction of the bore hole, pression in the bracket and arranged to be both in inclination and azimuth, and there must 1 clamped therein by means of a plate I0 having be further considered the magnetic -dip of the a cobperating spherical depression and arranged earths eld at the location where the core was Jto clamp the spindle 6 in adjusted'position by' l taken. It .will be obvious from a casual considermeans of clamp screws l2. The arrangement is 50 ation of the corrections necessary to the appar- Such that when the spindle 6 is at right angles ent dip and strike to secure the true dip and to the upper vsurface of the base plate-.2 it is` strike that the' problem is mathematically comtruly vertical. While the necessity for this is plicated and that calculations would be quite not imposed by the apparatus, it is desirable that j. subject to inadvertent errors due to mistakes in this be the case, because in the ultimate deterthe verticality of the spindle 6 when in its origin position.

The lower end of the spindle 6 is provided with an extension rod I4 having a pointed lower end designed `to cooperate with a scale I3, graduated as indicated, to show both the inclination of the spindle 6 and the azimuth .of thev inclination with respect to magnetic north.

The spindle 6 carries a sight tube I6 which is provided with two cross-hairs I8 and 20 arranged parallel to the axis of the spindle and in a common piane including the axis of the spindle.-

These cross-hairs are adapted to be aligned with .a wire 50 in the adjustment of the instrument,

as will be hereafter apparent.

Above the mounting 8 the spindle 6 carries a xed protractor plate 22, while above this plate there is mounted on the spindle for rotation about its axis a sleeve 24 carrying a pointer 26 cooperating with the graduations on the plate 22, which sleeve is adapted to be clamped in adjusted position by means of a thumb screw 28. The north marking on the plate 22 lies in the plane deiined by the cross-hairs I8 and 20. The sleeve 24 at its upper end carries a protractor 32 pivoted to it at 30 and carrying a plate 34 which represents the bedding plane of the strata shown in a re. In order to read the inclination of the protractor 32 relative to the axis of the spindle 6, there is provided a pointer 36,* preferably of a spring type, secured to the sleeve 24 at 38 and arranged 1 to be clamped by means of a thumb screw 40 against the protraotor 3 2 to hold it in adjusted position.

Brackets 42 support a yoke 44 for rotation about an axis passing horizontally through the center of universal support of the spindle 6. The mounting is preferably provided by removable screws so that, if occasion requires, the yoke may be removed. The yoke is counter-weighted, as indicated at 48, and provides an anchor for the upper end of a wire 50 which is connected through a tensioning spring 52 to a slide 54 mounted in a guideway 56 in the base 2 and arranged to be clamped in adjusted position therein by means of a screw 56. The center line of guide- Way 56 passes through the vertical line through the center of support of the spindle 6 and represents the direction of the Lhorizontal component of the earths magnetic eld, magnetic north being to the right, as indicated in Figure 1. The axis of support of yoke 44 is perpendicular to a verticalplanethrough the center line of the guideway 56. The arrangement is such .that the wire 5'0 extends along a line from the center of the groove 56 to the center of support Aof the spindle 6 so as to represent the actual direction of the magnetic field in both azimuth and dip, when the upper plane surface of the base 2 represents a horizontal plane at the location where the core under consideration was taken.

Since the line of the wire 50 and the axis of the spindle 6 will intersect in the center of support of the spindle, it will alwaysf'be possible to align the cross-hairs I6 and 20 and the wire 50 by rotation'of spindle 6 about its axis. Assuminghatthe spindle is located by adjustment of the-pointlof the member I4 on the scale I3 so that its inclinationand azimuth with respect to the horizontal plane represented by th'e upper surface of base 2 land the magnetic north, represent:

` edby the center line of slot 56, will correspond to the Values for a portion of a bore hole from which a core is taken, it will be clear that when the cross-hairs I8 and 20 and the wire 50 are aligned the representation of the component perpendicular to the axis of the bore hole of the magnetization of a core taken from such portion of a bore hole will necessarily lie in the plane defined by the axis of the spindle 6 and the wire 50, which will be the plane dened by the two cross-hairs I8 and 20. The north marking on the plate 22, being in the plane of the cross-hairs, will represent the direction of such component of the cores magnetic eld. The assumption is made, necessary in this procedure, that the polarization (or axis of maximum susceptibility) of the core corresponds to the prevailing direction of the earths magnetic field at the location where the core was taken.

f In the use of the apparatus, the starting pointis the data obtained from a magnetometer of the type indicated in the above mentioned Herrick patent. This will give the direction of the component of the magnetic field of the core perpendicular to the axis of the core, or, if the core is not polarized, the corresponding component of the axis of maximum susceptibility. There are also measured on the core the apparent dip and strike of a bedding plane shown in the core with mum susceptibility.

Assuming a polarized core, the slide 54 is adjusted in its slot 56 so that the inclination of the wire 50, as indicated by the scale along the slot 56, corresponds to the dip of the earths magnetic field at the location of the bore hole. Then the sleeve 24 is rotated to bring the pointer 26 in a position relative to the north indication on the plate 22 corresponding to the direction of dip of the bedding plane relative to themagnetic north of the core. With the sleeve secured in such position the protractor 32 is moved about its axis 38 dip of the bedding plane. The plate 34 will then represent in its relationship to the axis of spindle 4 muth being that relative to the magnetic northat the location of the bore hole.

Thenjwhile the axis of theispindle is maintained fixed, the spindle is rotated about its axis to line up the cross-hairs I8 and 2li with the wire 50, and the spindle is clamped in that position.'

It will be obvious that the results of the above manipulations will be the location of the'plate 34 in a position relative to the horizontal represented lby the upper face of support 2 and the magnetic north-south line represented by the center line of slot 56 corresponding precisely to the position of the bedding plane in its original state in the earth with .respect to the horizontal land also with respect to the horizontal component of theearths magnetic iield.l Accordingly, it is only necessary to measue the position of the plate 34 with respect to the horizontal and with respect to the axisof the slotl 56 .in order to 'determine the true dip and strike of the bedding plane with respect respect to a plane perpendicular to the axis of," the core and its magnetic north, or axis of maxi- `u .so that the pointer 36 will indicate o-n it's scale the amavis to the magnetic north, which can then be corrected by using the known magnetic declination to give the dip and strike with respect to the true north.

As indicated above the present apparatus avoids any errors due to neglect of the magnetic dip,

which may cause errors of considerable magnitude to arise in cases of substantial inclination of the bore hole in unfortunate directions, combined with equally unfortunate dipsl and strikes of bedding planes. Frequently the values of these factors are such as to cause hem to cancel each other to an extent rendering negligible the error arising from neglect of magnetic dip; but that is not always the case, and the present invention is designed to obviate any errors which may arise in any instance.

In case of a core showing anisotropic susceptibility only, the determinations will be correspondingly made though in such case two possible re-v sults will be secured, one of which must be chosen on the basis of other information.

It Will be obvious that various modifications in the embodiment of the invention may be made without departing from its scope; for example, the various markings may be made in other, but epivalent fashions, and mechanical details may also be substantially changed.

What I claim and desire to protect by Letters Patent is:

1. Apparatus for thedetermination of the dip and strike of a bedding plane indicated in a magnetically anisotropic core taken from abore hole, said apparatus' comprising means defining a horizontal plane at the position where the core was taken, means defining the azimuth and dip at said position of the earths magnetic vector relative to said plane, means universally pivoted relative to said plane-defining means for defining relatively to the' horizontal plane and magnetic vector the axis of the portion of the bore hole from which the core wastaken, means defining relative to said universally pivoted means the axial plane containing the axis of magnetic anisotropy of the core, and means defining the bedding plane of the core relative to the axis of the bore hole and the last named plane, said various means being relatively adjustable for the representation of the data belonging to diiferent cores and to represent the earths magnetic vector in said axial plane containing the axis of magnetic anisotropy of each core, whereby the relationship of said means dening the bedding plane and said means dening a horizontal plane and the earths magnetic vector may be made to represent a=rela tionship of the bedding plane vto the earth.

2. Apparatus for the determination of the dip and strike of a bedding plane indicated in a magnetically anisotropic core taken from a. bore hole,

said apparatus comprising a support havingv means for representation of a horizontal plane of the earths magnetic eld thereat, a member l universally pivoted on said support and adjustable to represent relatively to the support the axis of the portion' of the bore hole from which lthe core was taken, means on said member indicative of the direction of the component of the magneticiield of the earth perpendicular to the axis of the bore hole, means carried by the support` marking a line extending through the pivot point of said member and in the direction of. the earths magnetic iield relative to the reference data represented on the support, aligning means on said member to bring said indicated component of the magnetic iield of the earth perpendicular to the axis of the bore hole into the plane defined by the axis of said member and the line marked by said marking means, and an element adjustable on said member to indicate the relationship of said bedding plane to the axis of said member and said indicated component of the magnetic leld of the earth perpendicular to `the axis of the bore hole, whereby the relationship of said element to the support may be made to represent the relationship ofthe bedding plane to the earth.

3. Apparatus for the determination of the ,dip and strike of a bedding plane indicated in a magnetically anisotropic core taken from a borehole,

said apparatus comprising a support havingl means for representation of a horizontal plane at vthe position where the core was taken, and also of the direction .of the horizontal component of the earths magnetic iield thereat, a member universally pivoted on said support and adjustable to represent relatively to the support the axis of the portion of the bore hole from which the core was taken, Ameans on said Amember indicative of the direction of the component of the magnetic eld ofV the earth perpendicular to the axis of the bore hole, means carried by the support marking a line extending through the pivot point of said member and in the direction of the earths magnetic eld relative to the referf ence data represented on the support, sighting means on said member for observing -said line marking means to bring said indicated component of the magnetic ield of the earth' perpendicular to the axis of the bore hole into the plane dened by the ams of said member and v the relationship of said element to the support may be made to represent the relationship of the bedding plane to the earth. l

. JOHN M. PEARSON. 

